Many people have experienced back pain sometime in their lives. The causes of back pain are numerous. Some back pain is due to accidents, muscle strains, and sports injuries. But nowadays the most common cause is bad sitting habit. Sitting too long at a bad posture, for example, often happens with a computer operator or taxi driver in their daily activity. With correct posture such as standing or lying down, the spine is straight, and the internal pressure is equalized on all parts of the spine and muscles. On the other hand, with sitting with bad posture for several hours, the spine's internal pressure can rise up 5 times higher than that of lying down position. Such persisting pressure can lead to stiff muscles, limited circulation, and long term spine and bone damage.
A normal chair consists of three major components: The leg portion extended from the ground to a suitable height will provide support for the whole structure; The seat portion provides a comfortable flat surface to uphold the human body; The backrest portion provides another flat surface for the human torso to lean on. This basic structure has remained the same from ancient times. Alternatively, a chair without backrest is considered a stool, and a chair with an extra arm rest is called an armchair. Unfortunately, this basic structure gives little relief to back problems. As studies have shown, at an average sitting posture, the pressure on the lower back is 40 to 90 percent higher than that of standing posture, and several times higher than that of lying down posture. In some special cases, such as the person leaning notably forward to stare at the computer screen, the weight of his upper torso will be un-evenly distributed across his spine. Such awful posture increases the tension on his muscle, nerve and bone tissue, and speeds up the aging process. Over several years of exposure to excess pressure, a mid-aged person often experiences back pain, simply by sitting on the average chair for too long. Besides back problems, long sitting often causes other heath related issues, such as edema of lower legs, varicose veins, hemorrhoids, cold feet, and many other venous problems that can be attributed to sitting habits to a certain degree.
The most common type of advice that doctors give to patients with back problems is to refrain from the prolonged sitting posture in daily life. For example, some treatments include climbing a few stairs after half hour of desk work or walking around the building several times each day. All these will help to exercise the muscle around the back, increase blood flow and prevent fatigue, edema and various venous/muscle problems. Also, during walking, the pressure from the upper torso is evenly distributed on the spinal disc, as opposed to concentrated on a single spot during certain sitting positions. Hence the reduced pressure is less likely to cause damage to the disc. However, as an occupational hazard, several careers demand sitting for long period in work. For example, taxi drivers, truck drivers, or air traffic controllers all needs to sit for several hours in their daily work. In many other cases, the person working at a desk tends to forget advice from the doctors, and stay for hours before getting out of the chair. In U.S. Pat. No. 5,113,176, the author presents a lumbar roll device that can alert the user for poor posture or for sitting too long, and can remind the user for the need to exercise. Besides self performed exercises, a few other inventions proposed chairs that assist the user in exercising their lower back. These can typically be classified as ‘exercising chairs’. In U.S. Pat. No. 5,110,121, a chair that can exercise muscle on lower back based on spring resistance back pad and stationary lumbar support pad is introduced. In U.S. Pat. No. 7,377,889 B2, a general use chair that can provide a dynamic thrust motion to exercise the user's spine is proposed. U.S. Pat. Nos. 5,730,688 and 6,312,366, described abdominal-lumbar exercise devices that use flexible upright resilient members so that the user can exercise by pivoting against the resilience. U.S. Pat. No. 6,655,731 presents an orthopedic chair that includes a frame for supporting a contoured chair seat and back that rotate on a horizontal axis. This chair holds the person in a beneficial position for back support.
All the inventions mentioned above aim to exercise the muscle of the lower back, or alternatively, remind the user to quit sitting and engage in more exercise. However, if the user has already suffered a certain type of back spinal problem such as herniated disc, bulging disc, or is confined to the chair due to occupational requirements, the existing inventions provide little to help the situation. In this invention, we propose a new chair structure that can partially or completely lift the torso of the user from the chair, and hence reducing the weight asserted on the lumbar section of the spine. In this manner, we provide the relief on the spinal disc, and hence preventing any damage on it. The relief of pressure happens whenever the user sits in the chair, and does not require the user to engage in any voluntary exercise activity.